A dispenser closure widely used in Australia and other countries is described in Australian Patent Specification No. 446,218. Whilst generally satisfactory in use it has been known to leak particularly when the container is subjected to sudden shocks or a number of containers stacked one above the other. This particular dispenser closure suffers from the inherent disadvantage that effectiveness of the seal is dependent on the diaphragmatic transverse wall closure making sealing contact with a perpheral edge of the discharge spout which sealing contact can be broken by increasing pressure within the container.